Figure 13. --Test sample 

 loaded in boat. 



MAINTENANCE AND SAFETY 



The probes should be inspected before and after use for bends, cracks, and 



possible leaks. Each probe flange should be inspected to be sure it is still soldered 



to the probe. v Each probe cap should be inspected before and after use for torn O-rings 



and other visible damage. After each use all filters should be cleaned. The throttle 



valves should be cleared by blowing air through the valve in a. reverse direction. 



All hoses should be checked for cracks in the outer cover, damaged coupling threads, 

 and any inside obstructions before each use. Thermocouples need to be checked before 

 and after each use for physical damage. The temperature indicator may need recalibra- 

 tion once each year. The batteries should be charged before each use. Prior to each 

 use the relief valves next to the throttle valves should be checked with air pressure 

 to be certain they open at 100 psig (0.689 MPa) . The lifting frame and winch should 

 be inspected for loose bolts, kinks in tubes or plates, and fraying in the wire winch 

 rope. 



DISCUSSION 



The method described is capable of freezing a complete redd, the redd egg pocket, 

 or any portion of the redd. The individual sample size can be adjusted to provide a 

 more optimum determination of egg location, of the number of embryos and alevins in the 

 redd, of the timing of embryo development and fry emergence, the embryo and alevin 

 survival rate, and sediment particle size distribution by both vertical and horizontal 

 stratification. It will allow this type of analysis because the redd sample can be 

 dissected in its original state using a dissecting grid system. The equipment will 

 work under the conditions we have observed in salmon spawning areas if sufficient 

 access is available. 



The method has some of the same disadvantages that other freeze methods have. It 

 can smash embryos and alevins as the probes are being placed in the redd making it 

 difficult to separate natural from artificial mortality, and it kills all the embryos 

 and alevins in the sample. This can be very significant in streams having low runs of 

 salmonids and could preclude the use of taking the complete redd pocket. When you 



16 



